Mobile portable devices, such as cameras and/or mobile phones, use light emitting diodes (LEDs). In particular, LED-based flash lights or flash strobes use a relatively high current, which is provided to the LEDs. This high current is typically drawn from a low voltage storage capacitor or super-capacitor. This capacitor is charged during normal operation and used to provide the peak current during flash light periods. The low voltage super-capacitor generally introduces reduced peak current loading from the battery. In order to reduce the power losses, thermal stresses and solution size (in terms of circuit complexity) in the camera flash driver integrated circuit (IC), a desired pre-charged voltage for the super-capacitor must be determined and used. The desired pre-charge voltage for the super-capacitor is a function of the LEDs' electrical characteristics, such as forward voltage vs. forward current characteristic, which can have a wide spread over a large volume production. There are also other parameters that are considered, such as the upper threshold flash current level, the equivalent series resistance (ESR) in the discharge path, and the thermal performance of the camera flash driver IC from a system level perspective.
Some examples of conventional devices are U.S. Patent Pre-Grant Pub. Nos. 2004/0164685, 2006/0108933, 2005/0104542, 2007/0139317, and 2005/0248322; German Patent or Patent Appl. Nos. 102005012663, 10318780, 102005028403, 10393129, 102004034359, and 102005030123; and European Patent or Patent Appl. Nos. 1503430, 1511088, 1499165.